How to manage OS X Gatekeeper from the command line. Apple provides three basic settings for Gatekeeper in OS X Mountain Lion, but you can manage this service in finer detail if needed. Command Line Primer. Historically, the command line interface provided a way to manipulate a computer over simple, text-based connections. In the modern era, in spite of the ability to transmit graphical user interfaces over the Internet, the command line remains a powerful tool for performing certain types of tasks. Apple's Terminal provides you with a UNIX command line inside the OS X environment. You can enter the open command here to open any application, or to open a file with the application of your choice. There are several ways to adjust this command to suit your purposes, including the ability to host the application in your Terminal window.

• Running Mac Apps On Windows
• Mac Running App From Command Line Command

If you, like me, are an old-time Unix command-line fanatic now doing iOSdevelopment, you've probably wondered if you can build an iPhone app fromscratch, entirely outside of XCode. After all, Mac OS/X is a *nix,and all the familiar tools — Make, cc, ld — are all there. So,can you build and compile completely outside of XCode? As it turns out, yes,you can, and there are actually some speed advantages to doing so.

Now, before I continue — if you're looking to incorporate an automatedbuild system like Cruise Control or Hudson into your development process insupport of a development effort that normally works with XCode, you're probably far better off looking into the command-line tool xcodebuildthat ships as part of XCode. However, if you just want to throw togethera POC really quick, and you know your Objective-C syntax well enough thatyou don't really need the overhead of the XCode IDE (which can be quite a bit,in spite of Apple's impressive efforts to keep it manageable), you can compileand simulate an iPhone app using only command-line tools like we used to backin the day when men were men, women were women, and a compiler and a texteditor was all we needed.

XCode is pretty good about telling you what it's doing for you behind thescenes, as long as you know where to look. For example, you can see all ofthe build parameters that were run as part of a build by opening up the LogNavigator (Command+7) and clicking one of the 'build' logs as shown in figure1.

Figure 1: Viewing the build logs.

As you can see, there's a lot of stuff going on in there, and as itturns out, it's not all stuff you necessarily need.

The smallest iPhone app I can think of that (arguably) does something 'useful'is shown in listing 1 below.

Listing 1: window.m, A useful(?) iPhone app

This 'app' opens a window and displays 'Hello, World' as illustrated in Figure 2 (it also leaks its UIWindow instance because I didn'tcreate an autorelease pool. I hope your computer has enough memory tocompensate for this).

Figure 2: Hello, World

If you save this as, say window.m, you can compile and launchit (in the simulator) without ever starting up XCode.

Youmust have XCode installed — the simulator isn't distributedindependently of XCode and even the cross-compile libraries (which I'll detailfurther below) are part of the XCode bundle. However, you don't have tohave it running to compile and test an app.

LLVM, or Low Level Virtual Machine, is Apple's preferred Objective-C compiler these days. Ifyou've been doing iOS programming for a while, you probably know that it usedto all be done in gcc (and can still be done that way, if you're so inclined), but thedefault is LLVM (clang on the command line), so that's what I'll use here. clangis invoked from the command line just like gcc — you giveit an input file and an output file. I'll go ahead and create a Makefilefor this process; the first iteration is shown in listing 2.

Listing 2: Rough cut at a makefile

This fails (and honestly, you probably expected that) with:

If you have any experience with C programming, you can immediately seethe problem here; I didn't give the compiler a -I flag pointingto this header file. Interestingly, though, this minimal makefile didn't error on my importof <Foundation/Foundation.h> on line 1 — yet I didn't tellit where to find this include file. In fact, it would have compiled without complaining if I had given it an input that didn't require UIKit. For instance,listing 3 will compile just fine.

Listing 3: minimal.m, non-GUI objective-C class

minimal.m won't link, however, because although the header <Foundation/NSString.h> is found, the Foundationlibrary itself isn't. To include it, you have to specify the framework:

From a coding perspective,-framework works a lot like the -l flag in gcc.But — where didclang findNSString.h? It's not in /usr/include, or /usr/local/include — in fact, you'll search in vain fora file anywhere on your system named 'NSString.h' that's contained in adirectory named 'Foundation'. However, if you do look for 'NSString.h',you'll find a copy in /System/Library/Frameworks/Foundation.framework/Headers.But, by the strict 'rules' of C compilation, that can't be where clangresolved it, because it's not in a directory named 'Foundation'.This is another Objective-C extension to clang. In addition toregular header include searches (like /usr/include), there's thenotion of Framework searches. By default, clang will look under /System/Library/Framework for frameworks to include.Any such framework, if it has a Headers directory, will beresolved as Framework Name/header file. An ordinary iOSdeveloper would not need to know or care about such low-level details, butwhen you're working so close to the system core, it does matter.

So what are these 'frameworks'? Since NeXT's NeXTSTEP operating system andit's derivatives (Mac OS/X and GNUStep) are the only users of Objective C, it's sort of difficult to tease apart which parts ofclang are 'pure' Objective C and which parts are Mac OS/Xextensions. I believe, however, that this concept of a 'framework' is a nativepart of objective C. Essentially, a framework is a bundling of librariesand their headers and associated resources with built-in support for versioning.Anybody who's spent much time compiling and maintaining C-based packages ona Unix system can see how useful this is; the Linux community has been tryingto standardize on something like this with pkginfo and RPM's for quite a while.clang has a -l flag that will link ordinaryC libraries, but you'll likely never use this for iOS development.

So, what about UIKit? Well, it's not there under/System/Library/Frameworks. That's because it's not part ofMac OS/X; it's part of iOS. So how can you link to it? This is where thesimulator starts to come into play. XCode installs the iPhone simulator anda set of cross-compile libraries for you to build against. XCode has atendency to move things around from one version to the next, so you may haveto hunt around to find the 'core' directory, but as of XCode 4.6.1, thecross-compile libraries are found under:

Underneath this directory is another /System/Library/Framework,this time with a set of the Frameworks that iOS includes. (In fact, thisdirectory serves as the root directory of an entire iOS 'installation'). So,to get clang to compile an app that depends on UIKit, you haveto add this directory to the framework search directory. You do this viathe OS/X-specific '-F' flag to clang. So, the updated makefile looks likelisting 4:

Listing 4: First attempt at a cross-compile to iOS

The results are a little better, but this fails with:UIKit has a dependency on a framework called Core. This framework ispart of Mac OS/X, so clang finds it and tries to use it, butUIKit relies on a different version of Core thanthe one that Mac OS/X uses. The problem here is that clang is trying to resolve its frameworks from the simulatordirectory, but it's still finding headers under /usr/include. The UnixC programmer's solution, of course, is to add a '-I' as shown in listing 5.

Listing 5: Second attempt at a cross-compile to iOS

This gets us further, but the compiler now emits a lot of errors along thelines of:Again, clang is trying to generate a Mac OS/X executable whenwhat we want is an iOS executable. The solution is to add:In fact, with isysroot, you can get rid of the -Fand -I flags; this replaces the '/' directory as it pertainsto the compiler. Now, the compile completes, but the link step fails due to:This is because, although I've requested some cross-compile options, I stillhaven't actually asked for a cross-compile. I have to do that with:Almost there. This fails for me with a handful of 'Undefined symbols for architecture i386'. The reason is because I'm running on a 64-bit machine;to work around this, I have to addAnd voila! I get the executable file window. The completedmake file is shown in listing 6.

Listing 6: Successful attempt at a cross-compile to iOS

These are the fewest command-line parameters you can pass into clangand still get a working iOS executable.Now, how about running it? If I try to invoke it directly from the commandline, it predictably fails with:Which makes sense - I compiled something for iOS, but now I'm trying torun it on a OS/X. As you undoubtedly know, XCode includes an iPhone emulator,and you can invoke it from the command line and pass in an app to simulatewith the -SimulateApplication parameter. You can invoke itfrom the command line like this:(Notice the './' in front of the application name; if you omit this, the simulatorwon't find your executable).

So there you have it — without XCode running or open, I've compiledand tested a complete, working iOS app.Note that this whole process does not build an actual iPhone bundle.iPhone runs under an arm architecture, whereas this build, althoughit was a cross-compile, still runs on an intel processor. Tobuild for an actual deployment to an iphone, you'd have to change thearchitecture to arm, and to get it to install on a real device,you'd also have to deal with code signing. Still, it's interesting and funto see how far you can go without actually running XCode.

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Ah, I'm so sorry Anantha, I omitted a backslash from listing 6. It should read:

In fact, the backslashes in the code listing were there strictly for formatting reasons. So, you can jam all of this onto a single very long line; to simplify (but slightly uglify):

The line break after 'window.m' (as well as a hard-tab character) are required by the Make utility.

Running Mac Apps On Windows

Mac Running App From Command Line Command